1893-1981

American Chemist

Harold Clayton Urey is best known for his work with isotopes. He received the Nobel Prize for Chemistry in 1934 for the discovery and isolation of deuterium, a heavy isotope of hydrogen. He also played a major role in the development of the atomic bomb and made important contributions to the study of isotopes of a number of elements and to the theory of the origin of the planets.

After receiving his doctorate at the University of California at Berkeley, Urey worked with Niels Bohr (1855-1962) in Denmark. Returning to the United States, he held positions at Johns Hopkins University, Columbia University, the Institute of Nuclear Study, the University of Chicago, and the University of California.

Isotopes of an element have the same number of protons (i.e., atomic number) but a different number of neutrons—and, therefore, different mass numbers. Much...